This project proposes to study the regulation of lymphocyte growth in an in vitro system. Through an understanding of normal growth, we hope to elucidate some of the factors responsible for the maintainance of the abnormal growth patterns characteristic of the lymphocytic leukemias. The study will focus on ribosome synthesis and especially on post- transcriptional control of ribosome assembly as an important factor in growth regulation. We will, also, investigate the mechanisms for gene activation in stimulated intact cells and, particularly, in isolated nuclei. This phase of the project will include an attempt at isolation and characterization of intermediate factors which may carry the mitogenic stimulus from a cell surface receptor site to nuclear activating mechanisms. We will attempt to document the existence of blastogenic factors elaborated by stimulated lymphocytes. This will include further characterization of a factor elaborated by stimulated lymphocytes which is capable of activating resting monocytes. We will then explore the intracellular mechanisms governing the action of these factors. We will, further, continue to characterize leukemic lymphocytes by cell surface properties and by their capability of responding to phytohemagglutinin.